1. Field of the Invention
This invention relates generally to Emitter Locating Systems and, more specifically, to a Direction Finding Method and System Using Transmission Signature Differentiation.
2. Description of Related Art
Direction Finding (DF) Systems are used to find the direction towards emitting radio transmitters. But today's systems cannot automatically differentiate between two or more transmitters utilizing the same frequency (which can be a common situation). This leads to errors and false measurements. This invention provides a method of automatically resolving the ambiguity created by multiple DF transmitters transmitting on the same frequency, and then enabling the DF System(s)s to identify the transmitters' respective lines-of-bearing (LOBs).
The basic components of a DF System are: (1) a DF antenna array; (2) a DF receiver/processor (hereafter referred to simply as “DF receiver”); (3) some device to interpret the streaming Line-Of-Bearing (LOB) data sets from the DF Set; (4) some sensor device to determine the DF Set's location; and (5) some sensor device to output the DF Set's orientation relative to true North.
The major sources of measurement errors in real-world DF Systems are: (1) uncertainties from the DF antenna array due to frequency dependent variations; and (2) signal reflections, also known as multi-path. In practice though, multi-path typically represents the largest source of error. Where multiple transmitters are transmitting on the same frequency, the resultant confusion (in prior systems) is very similar to the confusion caused by large multi-path signals.
In today's DF Systems, multiple transmitters utilizing the same frequency would require an operator to manually distinguish between the resultant ambiguous readings. It should be further noted that with today's digital systems, it could be impossible to manually identify different transmitters utilizing the same frequency because these new digital transmissions have very short transmission periods.
The invention described herein uses an improved method and technique to intelligently process data from one or multiple DF Systems so that multiple transmitters radiating alternately on the same frequency can be distinguished—in an automatic fashion.
In conclusion, insofar as the inventor is aware, no invention formerly developed provides this unique application to resolve multiple radios transmitting on the same frequency in DF System measurements.